As magnetic storage densities of disk drives increase it is necessary that the magnetic recording layer of the storage media becomes thinner and that the separation between the magnetic recording layer and the transducer during relative motion becomes less. It will soon be necessary to maintain a separation of one microinch or less between the spinning disk media and the transducer without permitting head to disk or solid to solid contact that would quickly precipitate wear-out. One method for doing this is to maintain a thin layer of lubricant (in the range of 5 to 500 angstroms) on the disk surface with a thickness sufficient to prevent head to disk contact, but thin enough to ensure close spacing between head and disk. For this system, the disk is lubed (generally by dip or spin application) prior to assembly of the device. The lubricant is sufficiently viscous to assure that it is spun off the disk very slowly during drive operation. However, there is no lubricant that will last for the desired life of the device given only a one-time application. Therefore, some system for the replenishment of the film of lubricant at the disk surface is required.
To obtain successful and satisfactory replenishment of the disk recording surface lubricant film it is necessary that several objectives be met. The stored lubricant must be metered out at a rate within the desired range under all operating conditions to which the disk drive can be expected to be exposed. All of the lubricant that flows out of or is released from the reservoir must flow to the disk surface. This is to assure effective use of the stored lubricant and prevent waste that would be occasioned by droplets of lubricant that might be released from the reservoir without application to the disk surface. Further the circumferential distribution of the lubricant must be uniform and lubricant flow must be effectively zero when the device is not spinning.